Phase locked loops are known in the art. A phase locked loop is a circuit containing an oscillator whose output phase and/or frequency is steered to keep it in synchronization with some reference signal. A phase locked loop typically includes a phase comparator having a first input receiving an input reference signal, having a second input, and having an output, a filter having an input receiving the output of the phase comparator and having an output, an amplifier having an input receiving the output of the filter, and having an output defining the output of the phase locked loop, and a voltage controlled oscillator having an input receiving a control voltage from the amplifier and having an output connected to the second input of the phase comparator.
Phase locked loops have various applications. In many communications systems, for example, it is necessary to recover a clock signal from the received data. A phase locked loop is one way of recovering such a clock signal.